Weird Tranny issue

I ave a 97 c1500 with a 4.3 and an automatic transmission. Just under 160k. i have a pretty strange problem with the transmission. after i drive around 30 miles, shifting from 1st to second it slams into 2nd. if i restart the truck it shifts fine. its wierd because normally it shifts as smooth as a brand new truck. Im thinking do a flush and filter change. Im just cofused on this one because like i said when you restart the truck it wont do it

You have a very common problem and in fact the most common with the 4L60E. What is happening is the transmission is going into failsafe mode. When this happens the PCM raises the line pressure which gives you a harsh 1-2 shift. Probably a worn out TCC regulator valve in the valve body. Don't waste your money changing fluid. Instead go get your truck scanned for trouble codes.

My 97 z71 was doing that too right before i took it in to get the trans fluid changed.With my truck they guy broke open the trans filter and found all kinds of clutch packing in it. I replaced the trans and the truck still did it from time to time. I have a little over 50 k on the new trans and it does it every once in a while now but not as bad. When i talked to the shop that did my trans they said its normal.I dont think it is my self so if you take it in go to a shop you can trust.

You have a very common problem and in fact the most common with the 4L60E. What is happening is the transmission is going into failsafe mode. When this happens the PCM raises the line pressure which gives you a harsh 1-2 shift. Probably a worn out TCC regulator valve in the valve body. Don't waste your money changing fluid. Instead go get your truck scanned for trouble codes.

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ya i read about that after i posted this. i think i can replace the tcc and it wont be too bad